U.S. Pat. No. 5,796,214 filed on Sep. 6, 1996 by the present inventor, discloses ballast circuits using regenerative gate drive circuitry to control a pair of serially connected, complementary conduction-type switches of a dc-ac converter. Such switches may, for example, comprise an n-channel enhancement mode MOSFET and a p-channel enhancement mode MOSFET, for example. In the disclosed ballast, the phase angle between a resonant load current and a control voltage for the switches moves towards 0.degree. during lamp ignition, providing reliable lamp ignition.
It would be desirable to adapt the foregoing ballast to limit the output voltage at times when the potential for a high voltage exists, such as when a lamp is removed, or when end-of-life effects create the potential for high voltage situations.